Microbial Growth and Biofilms

Question 1

Eukaryotic microbes exhibit what type(s) of reproduction?

Answer 1

Sexual

Asexual

Question 2

Prokaryotic microbes exhibit what type of reproduction? What is it called?

Answer 2

Asexual reproduction

Binary fission

Question 3

Steps of binary fission

Answer 3

1. DNA replicates
2. Cell elongates and chromosomes separate
3. Septum forms
4. Cell divides

Question 4

FtsZ: homologue of what eukaryotic protein?

Answer 4

Tubulin

Question 5

FtsZ: what is it required for?

Answer 5

Cell division

Septum formation

Question 6

FtsZ: what does it form?

Answer 6

Contractile ring at midcell

Question 7

FtsZ: where does its energy come from?

Answer 7

Hydrolysis of GTP

Question 8

Growth curve: what does it show?

Answer 8

Growth of microbial population in culture

Question 9

Batch culture

Answer 9

Closed vessel, single batch of medium

Question 10

Growth curve: x axis

Answer 10

Time

Question 11

Growth curve: y axis

Answer 11

Log of number of viable cells

Question 12

Growth curve: lag phase

Answer 12

No growth yet

Cells are synthesizing new components

Question 13

Growth curve: exponential (log) phase

Answer 13

Balanced, constant growth

Question 14

Generation (doubling) time

Answer 14

Describes growth during exponential (log) phase: time required for cells to divide

Question 15

Growth curve: stationary phase

Answer 15

Population growth ceases

Question 16

Why do cells stop growing in stationary phase?

Answer 16

All nutrients are used up
Culture becomes too crowded/dense
Buildup of toxic byproducts
Oxygen gets used up

Question 17

Growth curve: death phase

Answer 17

Cells begin to die

Question 18

Spores: what are they? In what phase do they form? Is spore state reversible?

Answer 18

Spores are stress-resistant, dormant cells
Form in stationary phase
Spore state can be reversible

Question 19

Examples of bacteria that form spores

Answer 19

Bacillus

Clostridium tetani

Question 20

Measuring microbial growth: direct cell counts- what instruments used?

Answer 20

Uses counting chambers (Petroff-Hausser)

Question 21

Drawback to direct cell counts

Answer 21

Hard to differentiate living from dead cells

Question 22

Measuring microbial growth: viable cell counts- what method used? Unit of growth?

Answer 22

Plating

Colony forming units (CFUs)

Question 23

Measuring microbial growth: turbidity measurements- how does it work? What instrument used?

Answer 23

Microbial cells scatter light striking them
More turbid- more cells- more light scattered
Spectrophotometer

Question 24

Biofilms

Answer 24

Microbial communities attached to a surface and covered with a protective matrix

Question 25

Stage 1 of biofilm growth: planktonic cells

Answer 25

Free-living, often motile cells

Question 26

Stage 2 of biofilm growth: attachment

Answer 26

Planktonic cells attach to surface using pili and adherence proteins

Question 27

Stage 3 of biofilm growth: colonization- how it works, what is the result

Answer 27

``` Quorum sensing (density dependent cell-cell signaling) activates gene expression Genes make a matrix of polysaccharide, protein, and DNA ```

Question 28

Stage 4 of biofilm growth: maturation

Answer 28

Formation of mushroom with channels for nutrients and oxygen gradients

Question 29

Stage 5 of biofilm growth: dispersal

Answer 29

Mushroom opens and planktonic cells are reformed

Question 30

Examples of where biofilms can be found

Answer 30

Lake/pond Water line Implants such as hip replacements Body systems such as GI, eye, lung, etc.

Question 31

Intelligent implant to battle biofilms: how it works

Answer 31

Prevention of biofilm formation by putting sensor into implant that can detect bacteria and then release antimicrobial solution A few bacterial cells are easier to kill than many in a biofilm

Question 32

Dental plaque: what is it classified as? How many microbial species found?

Answer 32

Example of biofilm in mouth | Over 300 microbial species present

Question 33

Carries: what are they, how are they formed

Answer 33

Tooth decay | Bacterial fermentation -> acidic byproducts -> enamel erosion

Question 34

Bacteria that causes carries

Answer 34

Streptococcus mutans

Question 35

Periodontal disease: what causes it?

Answer 35

Microbial infection with inflammation and tissue destruction

Question 36

Bacteria that causes periodontal disease and has also been linked to Alzheimer's

Answer 36

Porphyromonas gingivalis